The present disclosure relates to a composition for a golf ball cover having high elasticity and backspin performance and to a golf ball including a cover formed using the composition.
Current premium level golf ball covers provided on golf balls commonly used by advanced amateur players or professional golfers may be formed using a dual layer cover including an external cover and an inner cover. In the dual layer cover described above, the inner cover is formed using a relatively strong, solid ionomer resin having a relatively high level of elasticity. The external cover is formed using a soft, durable polyurethane resin. In a case in which the dual layer cover is combined with a single core, a three-piece golf ball may be formed. In a case in which the dual layer cover is combined with a dual core, a four-piece golf ball may be formed.
As an ionomer having a relatively high level of strength and elasticity in order to primarily protect an inner core of an elastic body and to increase driving distance, an ionomer resin (‘Surlyn®’ by DuPont is commonly used) formed in such a manner that a polyethylene-acrylic acid copolymer is neutralized by a metal ion has been applied to use in a golf ball cover.
However, in a round of golf, not only driving distance, but also control performance (backspin power) capable of accurately stopping a golf ball on the green when a golf ball is hit with a short iron is critical. To this end, in the case of premium level golf balls, golf balls including a dual layer cover having an ionomer resin as an inner cover, as described above, and a polyurethane layer formed thereon as an external cover, have been manufactured. A polyurethane layer forming an external cover may have soft, durable properties. In the case of a polyurethane layer, it is easy to put backspin on a golf ball, so that a polyurethane layer is appropriate as a material for an external cover.
In terms of golf balls having a dual layer cover structure described above, given the current situation in which elasticity and spin force are simultaneously demanded, the use of a material described above is inevitable. Alternative materials simultaneously satisfying requirements for elasticity and the ability to impart spin force to substitute a material for the related art have not yet been developed.
In the meantime, golf balls having a dual layer cover structure may be manufactured in such a manner that an ionomer resin is first melted at a temperature of 200° C. or higher to be disposed on a core of a golf ball, in order to form an inner cover using injection molding; the inner cover is sufficiently cooled at room temperature for at least one day to evenly polish a surface thereof; and a urethane resin is cast using a casting method to form an external cover. As such, the manufacturing process of golf balls having a dual layer cover structure may be complicated and may require a significant amount of time, so that productivity thereof is relatively low.
In addition, in the case of golf balls having such a dual layer cover structure, a thickness of a dual layer cover is formed to be about 2 mm. An inner cover and an external cover are manufactured using two materials using two processes, so that a thickness of a cover layer may be increased to be greater than necessary. Such thicknesses of an inner cover and an external cover may affect the performance of golf balls. When thicknesses thereof are increased, the percentage of an inner core is relatively reduced. Thus, the overall performance thereof, such as feel, resilience, and back spin, may be degraded.
However, main materials of a dual layer cover formed using an ionomer and polyurethane have a certain level of limitations in reducing a thickness thereof, due to characteristics of a casting process in which the main materials are used.
Thus, novel materials, that is, materials simultaneously implementing elasticity and spin are demanded in various aspects.
The prior art related to an exemplary embodiment includes ‘Golf Ball Cover Composition,’ Korean Patent No. 0281227. The document described above describes a technique in which a polyester oligomer in a zirconia complex state and a zirconia filled state is added to an ionomer resin to be mixed and reacted therewith, so that a portion of unsaturated carboxylic acid in an ionomer resin may be neutralized to be another metal including zirconium and may be additionally polymerized to be an ester, in order to modify and transform an ionomer of the related art.